1. Field of the Invention
The present invention relates to a method and device for carrying out measurements and/or operations in a well at the level of the surrounding formations.
The invention is more especially applicable when it is a question of carrying out measurements and/or operations at the level of geological formations. In this case, the measurements made may comprise recording of the pressure and temperature at the bottom, the measurement (focused or not) of the electric resistivity, as well as acoustic, nuclear measurements, etc.
These measurements and operation techniques are well known by specialists and will not be described in greater detail here.
The measurements may be completed by displaying the walls of the well by means of television cameras, for example.
2. Discussion of the Prior Art
U.S. Pat. No. 4,349,072 discloses a device for carrying out measurements and/or operations in a well, this device comprising a tube open at its lower end and of a diameter less than that of the well, a measuring or operating (probe) instrument, movable by remote control from the surface between a first position where said instrument is housed in the lower part of the tube forming a protection casing and a second position in which said instrument leaves said tube at least partially at the lower end thereof so as to carry out the measurement or the operation, and an electric transmission cable equipped with a first electrical connection member adapted to be moved in the tube for joining up with a second electrical connection member coupled to said instrument.
According to this patent, the tube equipped with a probe is lowered into the well, then an extension is sent from the surface towards the probe to which it is secured. The assembly thus formed (probe plus extension) is then pumped so as to cause the probe to travel along the zone to be explored.
Such a tube requires then the lowering from the surface of a more or less long extension depending on the extent of the zone of the well to be explored. Furthermore, the further away the zone to be explored, the greater the length over which the extension must be conveyed. Thus, the tube is immobilized in its lower position for long periods of time. This represents high risks of the tube jamming in the well. These risks are increased if the well runs out of the vertical.
By the expression "out of the vertical wells" is meant here, as well as in the rest of the description, not only wells with a slight deflection but also greatly deflected or substantially horizontal wells.
It should be noted that the present invention may also be used in the vertical portions of the wells.
The prior art may be further illustrated by U.S. Pat. No. 4,064,939, 4,082,144 and 4,388,969 as well as by the European patent application No. 0,077,275.
This document describes a method which requires the extension to be sent by pumping through a tube from the surface as far as the position where measurements are to be carried out.
The drawbacks of the devices of the prior art are considerably reduced if not eliminated by using the method and device of the present invention for carrying out measurements and/or operations in a well.